The invention relates to a method for analysis of a high-temperature molten material using optical emission spectrometry. It is particularly suitable for the analysis of a molten metal, such as molten iron or steel, but can also be used to analyze slag, glass, lava, or any other fluid, high-temperature material. The invention also relates to a new device for the use of the inventive method for analysis using optical emission spectrometry. The invention furthermore relates to an immersion sensor for analysis of molten materials, particularly metal, slag, or lava melts, or of glass, comprising an immersion carrier, a radiation detector, a radiation guidance system for recording and further transmission of the radiation, and a signal interface located on or in the immersion carrier.
The preferred range of applications of the invention is the analysis of metal, lava, glass, or slag baths, and of other refractory molten materials, wherein the named materials are in a partially or fully molten state.
The areas in which the analysis of the composition of high-temperature molten products is performed are quite wide-ranging, i.e., having a temperature above 300° C., for example molten steel, molten aluminum, molten glass, or molten lava. The methods generally used require the removal of a sample, which is first cooled and then subjected to various analytical procedures after partial or complete cooling.
Different analytical techniques can be used and are selected depending on the components of the composition to be identified qualitatively or dosed quantitatively. This selection is dictated by the practical modalities in connection with operating conditions, such as the physical form in which the material to be analyzed is presented (e.g., steel bath in a steel refinery converter, bath of refractory material in a smelter, molten glass in an oven, or lava in a volcano), and the desired type of operation (e.g., practical access to the material, environment at the analysis location, available time before achieving results of the analytical procedure).
The present description, for purposes of explanation, concentrates on the area of analysis of metallic molten masses, while reserving the application of the method to other high-temperature molten materials.
In the context of analysis of molten metals, emission spectrometry is the most commonly used technique, because it can be performed very quickly, requires only very little work in preparation of samples, and enables the simultaneous dosage of a large number of components. Emission spectrometry is based on the fact that the material to be analyzed is excited in such a way that ionization of the material, of which it consists, is achieved. The radiation emitted is then analyzed in a spectrometer, which separates this radiation into different wavelengths corresponding to the materials present. A distinction is made between different types of spectrometer, wherein the most common in the areas in question are equipped with photomultiplier detectors or with CCD systems (Charged Coupled Device) or CMOS (Complementary Metal Oxide Semiconductors). The equipment for analysis with emission spectrometry is either laboratory equipment or portable equipment for analysis of immobile materials.
The economic interest in the method of spectrometric analysis is known and is commonly used in industry, since it enables the entire chain of metals manufacture to be tracked, controlled, and monitored. The pressure towards profitability naturally makes necessary the search for the simplest and fastest methods, which suitably cost the least relative to the profitability of the manufacturing processes.
In this search for profitability, several methods have been examined for the dosing of fluid metals while omitting the taking of samples, and are currently being developed in the laboratory or in the context of more or less highly developed testing on a pilot line.
The current methods consist of exciting the product remotely, for example using a laser beam, whereby the product then emits an induced radiation due to the excitation of the beam, which is analyzed by an emission spectrometer. The spectrometer is more or less removed from the glowing (radiating) product to be analyzed, and in fact is located according to the practical possibilities of application, for example the working conditions in a steel mill. The radiation proceeding from the product to be analyzed can be guided to the spectrometer in different ways, such as through a glass fiber, through a telescope, etc.
It is known that current developments are underway to miniaturize and simplify spectrometers in which a detector based on CCD technology is used, the costs of which will be low enough to enable profitable industrial use in a production context. The different technologies named above—both those already used in industrial production and those technologies currently under development—are all based on an element which is located outside the object of analysis, in order to create the excitation which generates the radiation to be spectrometrically analyzed. At present, this often requires the use of a laser system which is located in the vicinity of the object of analysis—for example in a metal bath located in a converter. In addition, the aforementioned laser system also requires different targeting equipment to direct the laser beam.
In practice in industrial production, it can be determined that the environmental conditions around the places of production of molten metals, such as steel works, and correspondingly for the analysis of lava around volcanoes, are very aggressive relative to the devices used for their monitoring. In this connection, optical devices are particularly sensitive. The result is that the use of the aforementioned laser equipment presents a source of technical problems, and any development regarding a broad and intensive industrial application of spectrometric analysis methods using excitation from equipment involving the radiation emitted by lasers is often prone to accidents and is very difficult.
Such techniques as immersion sensors for analysis in molten materials are known from International application publication No. WO 03/081287 A2. Here, a carrier tube is disclosed, which is immersed in molten aluminum. Within the carrier tube a lens system is arranged. At the upper end of the tube an optical fiber is arranged, which is connected through an optical system, on the one hand to a spectrograph and on the other hand to a laser. The radiation emitted from the melt is guided through the optical fiber to the spectrograph, and there, the radiation is analyzed in order to derive analytical results pertaining to the composition of the molten aluminum.